We propose to develop a vaccine for the prevention of a human sexually transmitted disease caused by Chlamydia trachomatis. Despite the magnitude of the public health threat from this bacteria, there is currently no FDA approved vaccine. Preliminary results suggest that lipid antigens produced by bacteria may be useful vaccine candidates. Human T lymphocytes specifically recognize bacterial lipids presented by CD1 cell surface proteins on antigen presenting cells. To develop a prophylactic vaccine, we are investigating whether C. trachomatis lipids, presented by CD1 proteins, constitute an effective vaccine in guinea pigs. Guinea pigs are the most appropriate small animal model because they more closely mimic humans in both their response to infection and in their CD1 proteins. PROPOSED COMMERCIAL APPLICATIONS: Each year there are at least half a million genital tract infections with C. trachomatis making this sexually transmitted disease the most common reportable disease in the US. The estimated cost of untreated chlamydial infections and their complications is $2 billion in the United States. This proposal describes how we intend to capitalize on recent research discoveries to guide identification and development of a lipid vaccine to prevent Chlamydial infection.